Malolactic Fermentation Timing and Color

The malolactic fermentation (MLF) is a key process in the production of red wines and some white wines. While it is commonly conducted after the completion of the alcoholic fermentation (sequential), it can also be induced at the same time where Oenococcus oeni is inoculated shortly after the beginning of alcoholic fermentation (AF). While a concurrent MLF is typically completed in a shorter time period than a sequential MLF, it is often avoided due to concerns over the production of excess acetic acid, loss of color, and competition with the fermentative yeast Saccharomyces cerevisiae. Finally, the impact of concurrent MLF on the organoleptic qualities of red wines is relatively unknown and may present an obstacle for the adoption of this practice. This project seeks to address some of these concerns and determine the impact of MLF timing on Pinot noir wine chemical and sensory properties. In addition, the use of nonSaccharomyces yeast during cold soaking and their potential impact on a concurrent MLF will be explored. Initial experiments assessed the production of acetaldehyde by six different non-Saccharomyces yeast under cold soak conditions. All yeast grew well during the six day simulated cold soak and significant differences in the amount of acetaldehyde produced were observed. T. delbrueckii Alpha produced the highest concentration of acetaldehyde (71.8 mg/L) while H. uvarum and M. fructicola Gaia produced the lowest. While M. fructicola Gaia had been used in previous cold soak experiments, we decided to use T. delbrueckii Alpha for future Pinot noir cold soak experiments due to the high production of acetaldehyde observed and the potential significance of this compound for color formation and stability. In 2022 Pinot noir wines were produced with and without cold soak, with and without T. delbrueckii Alpha, and with a concurrent or sequential MLF. AFs were completed in ten days or less while all MLFs were completed within fourteen days. Only minor differences in the time to completion of AF or MLF were observed between the treatments suggesting that the use of nonSaccharomyces yeast during cold soak did not have an impact on the concurrent MLF and that the concurrent MLF did not impact the performance of the AF. Wines are currently being filtered and bottled and will be assessed by a sensory panel in summer 2023. Color analysis of the wines is also underway as is analysis of acetaldehyde concentrations throughout cold soak, AF, and MLF. Findings from this study will help determine the implications of MLF timing and the use of a non-Saccharomyces yeast in conjunction with a concurrent MLF. This will allow strategies to be developed for the use of MLF and non-Saccharomyces yeasts to improve Pinot noir wine color as well as the impact on other sensory characteristics.